Generally, in order to manufacture a semiconductor integrated circuit, various kinds of heat treatment, such as a film deposition process, an anneal process, an oxidization diffusion process, a sputtering process, an etching process and a nitriding process may be repeatedly performed on a silicon substrate such as a semiconductor wafer a plurality of times.
Since yield rate and quality of semiconductor manufacturing processes can be improved, the RTP technology to rise and drop the temperature of the wafer (object to be processed) has attracted attention. A conventional RTP apparatus generally comprises: a support ring (may be referred to as a guard ring, a heat uniforming ring, etc.) on which an object (for example, a semiconductor wafer, a glass substrate for photograph masks, a glass substrate for a liquid-crystal display or a substrate for optical discs) to be processed is placed; a single-wafer chamber (process chamber) for accommodating those parts; a quartz window disposed in the process chamber; heating lamps (for example, halogen lamps) arranged above or above and under the quartz window; and a reflector (reflective board) arranged at the opposite side of the object to be processed with respect to the quartz window.
The reflector is made of aluminum, for example, and gold plating is typically given to a reflective part thereof. A cooling mechanism (a cooling pipe, etc.) is provided so as to prevent temperature breakage of the reflector (for example, exfoliation of gold plating due to a high temperature) and also to prevent the reflector from being an obstacle of cooling the object to be processed at the time of cooling.
The quartz window may be in the shape of a board. When a negative pressure environment in the process chamber is maintained by evacuating gasses in the process chamber by a vacuum pump, the board-like quartz window has a thickness of several tens millimeters (for example, 30 to 40 mm) so as to maintain the pressure difference between the internal pressure and the atmospheric pressure. The quartz window may be formed in a pressure-resistant curved shape having a reduced thickness so as to prevent generation of a thermal stress due to temperature difference generated by a temperature rise.
A plurality of halogen lamps are arranged so as to uniformly heat the object to be processed, and the reflector reflects the infrared rays irradiated from the halogen lamps toward the object to be processed. In recent years, a demand for a rapid temperature rise (doe example, more than 100° C./sec) of RTP has been increased so as to achieve a high-quality process of an object to be processed and improve a throughput. The temperature rising rate depends on a power density of a lamp and a directivity of light irradiation from the lamp to an object to be processed. Here, the halogen lamp can be generally classified into a single-end lamp having a single electrode and a double-end lamp having two electrodes (such as a fluorescent lamp).
The single-end lamp has a light-emitting part extending vertically to an object to be processed, and the directivity and the energy efficiency thereof are maximized with respect to the object to be processed located underneath in a case of a single end lamp 2 having a single electrode part 3 like a bulb when a degree of an angle α of inclination of a reflector 4 relative to the lamp 2 is set to 45 degrees as shown in FIG. 1. Here, FIG. 1 is an illustration for explaining the inclination angle of the reflector 4 when the directivity and the energy efficiency are maximized in a case in which an object to be processed underneath is heated by a radiation light of the single end lamp 2. However, if the reflector 4 having an inclination angle of 45 degrees is provided around each of a plurality of lamps 2, the lamps cannot be arranged closed to each other, which causes a decrease in the power density. Thus the inventors considered to achieve a rapid temperature rise as a whole by increasing the lamp density by setting the inclination angle greater than 45 degrees as shown in FIG. 2 so as to set the inclination angle equal to or close to 90 degrees while slightly sacrificing the directivity and energy efficiency. However, it was found that, in such a structure, the light emitted from a middle portion 2a of the lamp 2 (filament) is reflected by the reflector 4a many times until the light is irradiated onto the object to be processed, and, thus, the efficiency of the energy irradiated onto the object to be processed is reduced to 40%.
On the other hand, the double-end lamp has a lower cost than the single-end lamp, and is superior to the single-end lamp in economical efficiency. Moreover, since the double-end lamp can be arranged parallel to the object to be processed as shown in FIG. 3, the radiation light can reach the object to be processed with less number of times of reflection than the single-end lamp by arranging the reflector above the lamp, and, thus, the energy efficiency reaches 60% which is higher than that of the single-end lamp. However, as disclosed in U.S. Pat. Nos. 5,951,896 and 4,857,704 and Japanese Patent Publication No. 5-42135 and Japanese Laid-Open Patent Application No. 2001-210604, the conventional technique attempts uniform irradiation to the object to be processed by arranging a plurality of sets of double-end lamps in multiple stages so that the light-emitting parts intersect with each other, a plurality of bar type double-end lamps being arranged in parallel in the same plane without using reflectors.
The process chamber is typically connected to a gate valve on a sidewall thereof so as to carry in and out the object to be processed, and is also connected to a gas supply nozzle at the sidewall for introducing a process gas used for heat treatment.
Since the temperature of the object to be processed affects the quality of process (for example, a thickness of a film in a film deposition process, etc), it is necessary to know the correct temperature of the object to be processed. In order to attain high-speed heating and high-speed cooling, a temperature measuring device which measures the temperature of the object to be processed is provided in the process chamber. Although the temperature measuring device can be constituted by a thermocouple, there is a possibility that the processed body is polluted with the metal which constitutes the thermocouple since it is necessary to bring the thermocouple into contact with the object to be processed. Therefore, there is proposed a payrometer as a temperature measuring device which detects an infrared intensity emitted and computes a temperature of an object to be processed from the back side thereof based on the detected infrared intensity. The payrometer computes the temperature of the object to be processed by carrying out a temperature conversion by an emissivity of the object to be processed according to the following expression:Em(T)=εEBB(T)  (1)where, EBB(T) expresses a radiation intensity from a black body having the temperature T; Em(T) expresses a radiation intensity measured from the object to be processed having the temperature T; ε expresses a rate of radiation of the object to be processed.
In operation, the object to be processed is introduced into the process chamber through the gate valve, and the peripheral portion of the object to be processed is supported by a holder. At the time of heat treatment, process gases such as nitrogen gas and oxygen gas, are introduced into the process chamber through the gas supply nozzle. On the other hand, the infrared ray irradiated from the halogen lamps is absorbed by the object to be processed, thereby, raising the temperature of the object to be processed.
However, although the support ring, on which an object to be processed (foe example, a silicon substrate) is placed, is formed of ceramics (for example, SiC) having excellent heat resistance, there is a difference in temperature rise of both parts due to a difference in heat capacity. Thus, the temperature rising rate of the object to be processed at a periphery thereof is smaller than that of the center. Such an influence has become remarkable as rapid temperature rise has been improved recently. In other words, in order to raise a temperature quickly and uniformly over the entire surface of the object to be processed, there is a problem that a mere uniform irradiation to the object to be processed is insufficient.
As a means for solving such a problem, the inventors considered a temperature control system in which temperatures of the center and the periphery of the object to be processed are measured so as to partially turn on the lamps so as to raise the temperature of only the periphery when the temperature of the periphery is lower than the center. However, the conventional arrangement of the double-end lamps disclosed in the above-mentioned patent documents has an object to uniformly irradiate the object to be processed, and it is not an object to irradiate partially an arbitrary part of the object to be processed. Thus, the arrangement of the lamps in the patent documents has difficulty in temperature controlling, and the center of the object to be processed is heated even if an attempt is made to heat only the periphery of the object to be processed. Additionally, since a reflector is not used (or cannot be used) in the arrangement of the lamps disclosed in the patent documents, the energy efficiency is low, and a service life of the lamps is shortened if a high voltage if applied to the lamps so as to maintain a power.